In general, antennas are classified as "directional" (sending and receiving in one specific direction) or "omnidirectional" (same sending and receiving qualities all around the antenna).
---A directional antenna has to be pointed in the direction of the closest base station for best performance. Mount it as high as possible and make sure it has best line of sight. Examples for directional antennas are directional sector panel antenna, yagi antennas, LPDA, directional wall mount antennas, grid parabolic antennas etc.
---An omnidirectional antenna does not require alignment with the closest base station. It will automatically connect to the closest tower. This allows for easy installation and only requires to be mounted as high as possible. Examples for omnidirectional antennas are ceiling mount antennas, camouflage antennas, fiberglass antennas, magnetic base antennas, patch antennas, rubber antennas etc. terminal antennas.
(3)Directional vs. Omnidirectional Antennas, When to use What
The main issue is how good your signal is outside. Directional antennas in general have higher gain than omnidirectional. The rule of thumb is:
---If you have a reasonably good signal outside (say 2-3 bars), use an omnidirectional antenna. It is easy to install and you don't have to worry about where the closest base station is located.
---If the signal is pretty bad also outside (1-2 bars), use a directional antenna.